Power conversion circuit and power conversion system

Abstract

A power converter, includes a first terminal and a second terminal which are connected to a direct current; a third terminal connected to an alternating current; N multi-level bridge arms connected in parallel to the first terminal and the second terminal, where the N multi-level bridge arms work in a parallel-interleaved manner, each multi-level bridge arm of the N multi-level bridge arms includes an alternating current node, and multiple time-varying levels are generated at the alternating current node, where the multiple levels are more than two levels; and a coupling inductor, including N windings coupled by one common magnetic core, where one end of each winding of the N windings is connected to an alternating current node of one multi-level bridge arm of the N multi-level bridge arms, and the other end of each winding of the N windings is connected to the third terminal.

What is claimed is: 
     
       1. A power conversion circuit, comprising:
 a first terminal and a second terminal, which are configured to connect to a direct current; 
 a third terminal, configured to connect to an alternating current; 
 N multi-level bridge arms, connected in parallel between the first terminal and the second terminal, and configured to work in a phase-interleaved manner so as to generate multiple time-varying levels at an alternating current node of each multi-level bridge arm of the N multi-level bridge arms, wherein the multiple time-varying levels for each alternating current node comprise more than two levels, and wherein N is an integer greater than or equal to three; 
 a coupling inductor, comprising N windings coupled by one common magnetic core, and configured to form inductances coupled with each other, wherein one end of each winding of the N windings is connected to a corresponding alternating current node of one multi-level bridge arm of the N multi-level bridge arms, and the other end of each winding of the N windings is connected to the third terminal; 
 a driving circuit, configured to generate driving signals to control the N multi-level bridge arms to work in a 360/N-degree-phase-interleaved manner within a switching cycle of the driving signal of the power conversion circuit, wherein phases of driving signals for adjacent multi-level bridge arms of the N multi-level bridge arms are spaced by a same angle, wherein the phase spacing angle corresponds to 360/N degrees; 
 a bleeder circuit, connected between the first terminal and the second terminal, and configured to bleed down a voltage of the direct current; and 
 a filter circuit, configured to filter the alternating current, wherein the filter circuit comprises a capacitor, wherein one end of the capacitor is connected to the third terminal and the other end of the capacitor is connected to a neutral point of the bleeder circuit, wherein the neutral point of the bleeder circuit is connected to the N multi-level bridge arms. 
 
     
     
       2. The power conversion circuit according to  claim 1 , wherein the common magnetic core comprises N interconnected cylinders, and the N windings wind around the N cylinders respectively in a same winding direction. 
     
     
       3. The power conversion circuit according to  claim 1 , wherein the N windings have the same number of turns. 
     
     
       4. The power conversion circuit according to  claim 1 , wherein the driving signals have a duty cycle within multiple preset ranges. 
     
     
       5. The power conversion circuit according to  claim 1 , wherein the multi-level bridge arms are M-level bridge arms, and the N multi-level bridge arms generate (M−1)*N+1 levels. 
     
     
       6. The power conversion circuit according to  claim 1 , wherein each multi-level bridge arm of the N multi-level bridge arms is a neutral-point-clamped multi-level bridge arm; and
 wherein the neutral point of the bleeder circuit is connected to a clamped neutral point of each multi-level bridge arm of the N multi-level bridge arms. 
 
     
     
       7. The power conversion circuit according to  claim 1 , wherein the multi-level bridge arms are capacitor-clamped multi-level bridge arms. 
     
     
       8. A three-phase power converter, comprising:
 a three-phase power conversion circuit, configured to perform power conversion between a three-phase alternating current and a direct current, wherein each phase of the three-phase power conversion circuit comprises:
 a first terminal and a second terminal, which are configured to connect to a direct current; 
 a third terminal, configured to connect to an alternating current; 
 N multi-level bridge arms, connected in parallel between the first terminal and the second terminal, and configured to work in a phase-interleaved manner so as to generate multiple time-varying levels at an alternating current node of each multi-level bridge arm of the N multi-level bridge arms, wherein the multiple time-varying levels for each alternating current node comprise more than two levels, and wherein N is an integer greater than or equal to three; 
 a coupling inductor, comprising N windings coupled by one common magnetic core, and configured to form inductances coupled with each other, wherein one end of each winding of the N windings is connected to a corresponding alternating current node of one multi-level bridge arm of the N multi-level bridge arms, and the other end of each winding of the N windings is connected to the third terminal; and 
 a driving circuit, configured to generate driving signals to control the N multi-level bridge arms to work in a 360/N-degree-phase-interleaved manner within a switching cycle of the driving signal of the power conversion circuit, wherein phases of driving signals for adjacent multi-level bridge arms of the N multi-level bridge arms are spaced by a same angle, wherein the phase spacing angle corresponds to 360/N degrees; 
 
 a bleeder circuit, connected between the first terminal and the second terminal of each phase of the three-phase power conversion circuit, and configured to bleed down a voltage of the direct current; and 
 a three-phase filter circuit, comprising three capacitors and configured to filter the three-phase alternating current, wherein one end of each capacitor of the three capacitors is connected to the third terminal of one phase of the three-phase power converter circuit, and the other ends of the three capacitors are connected together to a neutral point of the bleeder circuit, wherein the neutral point of the bleeder circuit is connected to each phase of the three-phase power conversion circuit. 
 
     
     
       9. The three-phase power converter according to  claim 8 , wherein the common magnetic core comprises N interconnected cylinders, and the N windings wind around the N cylinders respectively in a same winding direction. 
     
     
       10. The three-phase power converter according to  claim 8 , wherein the N windings have the same number of turns. 
     
     
       11. The three-phase power converter according to  claim 8 , wherein the driving signals have a duty cycle within multiple preset ranges. 
     
     
       12. The three-phase power converter according to  claim 8 , further comprising:
 a first neutral, configured to connect to a neutral of a grid, wherein the first neutral is connected to the ends of the three capacitors that are connected together. 
 
     
     
       13. A power conversion system, comprising:
 M power conversion circuits, configured to perform power conversion between an alternating current and a direct current, wherein each power conversion circuit of the M power conversion circuits comprises:
 a first terminal and a second terminal, which are configured to connect to a direct current; 
 a third terminal, configured to connect to an alternating current; 
 N multi-level bridge arms, connected in parallel between the first terminal and the second terminal, and configured to work in a phase-interleaved manner so as to generate multiple time-varying levels at an alternating current node of each multi-level bridge arm of the N multi-level bridge arms, wherein the multiple time-varying levels for each alternating current node comprise more than two levels, and wherein N is an integer greater than or equal to three; and 
 a coupling inductor, comprising N windings coupled by one common magnetic core, and configured to form inductances coupled with each other, wherein one end of each winding of the N windings is connected to a corresponding alternating current node of one multi-level bridge arm of the N multi-level bridge arms, and the other end of each winding of the N windings is connected to the third terminal; and 
 
 a driving circuit, configured to generate driving signals to control the M power conversion circuits to work in a 360/(N*M)-degree-phase-interleaved manner within a switching cycle of the driving signal of the power conversion circuit, wherein phases of driving signals for adjacent multi-level bridge arms of the N multi-level bridge arms of the M power conversion circuits are spaced by a same angle, wherein the phase spacing angle corresponds to 360/(N*M) degrees; 
 a bleeder circuit, connected between the first terminal and the second terminal of each power conversion circuit of the M power conversion circuits, and configured to bleed down a voltage of the direct current; 
 a fourth terminal; 
 a coupling inductor, comprising M windings coupled by one common magnetic core, and configured to form inductances coupled with each other, wherein one end of each winding of the M windings is connected to the third terminal of one power conversion circuit of the M power conversion circuits, and the other end of each winding of the M windings is connected to the fourth terminal; and 
 a filter circuit, connected to the fourth terminal and configured to filter the alternating current, wherein the filter circuit comprises a capacitor connected on one end to the fourth terminal and on the other end to a neutral point of the bleeder circuit, wherein the neutral point of the bleeder circuit is connected to each power conversion circuit of the M power conversion circuits; 
 wherein M is an integer greater than or equal to two.